Correct oil capacity of a 1977 OMC 175 engine

The OMC 175 engine is a Ford 302 engine block and everything I know and read suggests this should be 5 quarts oil capacity. But, the Dip stick is stamped "Capacity 4 quarts." My maintenance manual doesn't really address this either.

I have real concern for this as I have been having radical oil pressure readings on the gauge and the other day, when the dip stick read 1 quart low, I experienced a lifter that started rattling. If the capacity is really 5 quarts, I was running with 2 quarts low which would explain a lot of my concern.

Does anyone have a reading about this? Is the capacity 5 quarts, or 4 quarts. I feel reasonably confident it is the correct dip stick.....but who knows.

Thanks

Re: Correct oil capacity of a 1977 OMC 175 engine

This is just a thought and not from any particular expertise on the engine, but the dipstick marking may be for pan capacity only and not include external "plumbing" or filter capacity.

Re: Correct oil capacity of a 1977 OMC 175 engine

My S-10 4.3 holds close to 5 qts. My OMC 4.3 holds 4. Next time you change the oil just put in 4, start her up and let things circulate, then check the level. Add as needed.

Re: Correct oil capacity of a 1977 OMC 175 engine

I have a 175 too, 5 quarts is too much.

I have made that mistake before as well, its right around 4 for my OMC 302

Re: Correct oil capacity of a 1977 OMC 175 engine

One quart low would not cause your lifter chatter. The oil pick up is in the very lowest spot in the pan. Better keep an eye the lifter situation. My oil presure is kinda radical until I'm cruising.

Re: Correct oil capacity of a 1977 OMC 175 engine

I had a '75 190 hp 302, now a 5.0 roller cam with the same dipstick and oil pan. Making sure that I level the engine, they both took 5 quarts, w/ new filter, to the full mark on the OEM dipstick. My dipstick has no capacity stamped on it.

The 175 hp 302 was the identical motor with a different cam.

Re: Correct oil capacity of a 1977 OMC 175 engine

hmm , maybe some different pans then.

cuz when I put 5 quarts in mine, I was a solid half inch above the fill line on the dipstick.

Re: Correct oil capacity of a 1977 OMC 175 engine

Ayuh,.... Levinz11 has Got it,.... Drain it, add 4 qts., run it, then check it, 'n fill to the full mark,...

'n I agree with REDRIG,.... there's a BaZillion different pans out there,...

Re: Correct oil capacity of a 1977 OMC 175 engine

Thanks guys, I am headed out to tackle this problem and will report my findings.

My long term concern about this is that regardless of the rpm's, the oil pressure reading bounces around...running at 40-50psi for a while, then if I change the rpm slightly it may drop down for a while 20psi, never dropping below that level, then it may bounce back up to 40-50 psi. My assumption has been that the oil pickup screen might be plugged and I have changed oil at least 4 times the past year after running various cleaning additives through. (The previous owner abused the maintenance requirements and there was a lot of sludge in there.)

However, with the new lifter clatter that came and went on my last run, this presents me with new anxiety. So, here is my plan.

Having forgotten how much oil it took at last oil change...old age I guess, I will do the exercise of measuring with the engine level as you folks suggest and try to put this issue to bed..

I will be replacing the oil pressure sender in hopes I see a more constant reading.

I will crack open the old oil filter looking for metal filings or something disastrous.

One other issue, while this engine has good compression on all cylinders and burns little oil, (last time I checked) I have accepted a small amount of leak from bearing seals being this engine is so old, and have been skeptical about using a lot of sludge cleaning products for fear of destroying what is left of them. In a panic mode having the lifter clatter, I took advice of an advocate for "Marvel Mystery Oil" (or whatever it is called) and a quart of that is in the engine...I haven't run it since I installed it, but was interested in what you folks think about it.

Re: Correct oil capacity of a 1977 OMC 175 engine

RogerBoat said:

Thanks guys, I am headed out to tackle this problem and will report my findings.

My long term concern about this is that regardless of the rpm's, the oil pressure reading bounces around...running at 40-50psi for a while, then if I change the rpm slightly it may drop down for a while 20psi, never dropping below that level, then it may bounce back up to 40-50 psi. My assumption has been that the oil pickup screen might be plugged and I have changed oil at least 4 times the past year after running various cleaning additives through. (The previous owner abused the maintenance requirements and there was a lot of sludge in there.)

However, with the new lifter clatter that came and went on my last run, this presents me with new anxiety. So, here is my plan.

Having forgotten how much oil it took at last oil change...old age I guess, I will do the exercise of measuring with the engine level as you folks suggest and try to put this issue to bed..

I will be replacing the oil pressure sender in hopes I see a more constant reading.

I will crack open the old oil filter looking for metal filings or something disastrous.

One other issue, while this engine has good compression on all cylinders and burns little oil, (last time I checked) I have accepted a small amount of leak from bearing seals being this engine is so old, and have been skeptical about using a lot of sludge cleaning products for fear of destroying what is left of them. In a panic mode having the lifter clatter, I took advice of an advocate for "Marvel Mystery Oil" (or whatever it is called) and a quart of that is in the engine...I haven't run it since I installed it, but was interested in what you folks think about it.

Click to expand...

I have an old Jeep (91) with a couple hundred thou on her. The lifter chatter on a cool morning is down right impressive. It usually stops by the end of my short street once things get moving. You know what really quiets her down, though? Marvel Mystery Oil. I think Boomyal has recommended this stuff as well. I replace one qt of oil with one qt of MMO. When the trip ODO gets up to 3000 miles that damn chatter returns and I know its time to replace.

I don't sweat it too bad. Old motors make old motor sounds.

Re: Correct oil capacity of a 1977 OMC 175 engine

RogerBoat said:

Thanks guys, I am headed out to tackle this problem and will report my findings.

My long term concern about this is that regardless of the rpm's, the oil pressure reading bounces around...running at 40-50psi for a while, then if I change the rpm slightly it may drop down for a while 20psi, never dropping below that level, then it may bounce back up to 40-50 psi. My assumption has been that the oil pickup screen might be plugged and I have changed oil at least 4 times the past year after running various cleaning additives through. (The previous owner abused the maintenance requirements and there was a lot of sludge in there.)

However, with the new lifter clatter that came and went on my last run, this presents me with new anxiety. So, here is my plan.

Having forgotten how much oil it took at last oil change...old age I guess, I will do the exercise of measuring with the engine level as you folks suggest and try to put this issue to bed..

I will be replacing the oil pressure sender in hopes I see a more constant reading.

I will crack open the old oil filter looking for metal filings or something disastrous.

One other issue, while this engine has good compression on all cylinders and burns little oil, (last time I checked) I have accepted a small amount of leak from bearing seals being this engine is so old, and have been skeptical about using a lot of sludge cleaning products for fear of destroying what is left of them. In a panic mode having the lifter clatter, I took advice of an advocate for "Marvel Mystery Oil" (or whatever it is called) and a quart of that is in the engine...I haven't run it since I installed it, but was interested in what you folks think about it.

Click to expand...

Ayuh,..... Two Thoughts,...

Insteada replacin' the sender, remove it, add a T fittin', 'n a mechanical gauge,....
Then you can cross check 'tween the gauges, 'n see if 1 is lyin',...

Use pipe dope paste, Not tape,...

Ya need to maintain Ground continuity, for the sender to work right, which might be the present problem,...

The Marvels won't hurt anything, but I prefer just plain ole good clean motor oil, in whatever flavor yer comfortable with,...

Snake oil additives, are just That,...

Btw,... Marvels is designed to be added to yer Fuel, for upper cylinder lube,...

Re: Correct oil capacity of a 1977 OMC 175 engine

Just wanted to update the results of your advice, I did the Tee and added a manual pressure guage....turns out I am running a constant 45 lbs. pressure at all rpm's then drops down at idle to 20 lbs. when the oil is hot. Guess I am relieved, thanks for the advice. The sender is bad, I have tried two new units from the auto supply, but they aren't in sink with the dashboard gauge. I think I found the correct unit on the internet so will order that. As far as the correct oil capacity, I haven't yet changed oil, I was impressed with the cleaning ability of the "Mystry Oil", and whether it's all in my mind or not, I get the impression the engine is running a little better than before so decided to run the boat a little longer before changing oil. Thanks for the advice guys, really helps to bounce concerns off other people.